This application claims the priority of Korean Patent Application No. 2002-0060046, filed on Oct. 2, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a power supply device and a method having a spark prevention function, and more particularly, to a power supply device and a method capable of preventing sparks occurring in situations when an external device is connected to the power supply device in operation.
2. Description of the Prior Art
Power supply devices refer to devices supplying power to external devices connected thereto. Such power supply devices include a rectifier for obtaining direct current (DC) voltages by smoothing currents from an external alternating current (AC) power source, an uninterruptible power supply (UPS) for continuously supplying AC electric power of good quality to external devices against power failure, short power outage, voltage fluctuation, frequency fluctuation, and so on, and a frequency converter capable of providing diverse voltages or frequencies at any values by using a microprocessor and the like.
FIG. 1 is a view for illustrating a conventional power supply device.
Referring to FIG. 1, a power supply device has a filter 12, a rectifier 14, a field effect transistor (FET) 16, a switching controller 18, a transformer 20, a output rectifier 22, a feedback circuit 24, output connectors 26, and so on.
The filter 12 supplies AC power to the rectifier 14, eliminating surge and noise voltages flowing in from an AC power source 10, and the rectifier 14 is constructed with bridge diodes D1, D2, D3, and D4 and a capacitor C1 and rectifies an AC power inputted from the AC power source 10. A voltage rectified by the rectifier 14 is applied to a primary coil of the transformer 20, and the transformer 20 induces a voltage across a secondary coil thereof through interactions of the primary and secondary coils. At this time, the FET 16 is turned on and off by the controls of the switching controller 18 so that currents flowing in the primary coil of the transformer 20 are controlled, to thereby control the induction of a voltage across the secondary coil of the transformer 20. A voltage induced in the second coil of the transformer 20 is rectified and smoothened in the output rectifier 22 so that a DC voltage is finally outputted through the output connectors 26. At this time, the feedback circuit 24 detects an output voltage of the output rectifier 22 and feeds back the detected output voltage to the switching controller 18, and the switching controller 18 controls switching operations based on the fed-back voltage to constantly maintain the output voltage.
However, if an external device is connected to the output connectors 26 during the operations of the power supply device, a large amount of current instantly flows since a normal output voltage of certain level is outputted across the output connectors 26 and the external device connected to the output connectors 26 has a voltage of lower level than the normal output voltage. In this situation, a contact resistance value between the output connectors 26 and the external device increases since a contact area therebetween is considerably small. Therefore, a voltage becomes large with the abrupt current increase and the resistance value increase, and power instantly consumed is increased due to the increased voltage and current, which generates sparks or arc. Such spark occurrences lead the power supply device and the external device to malfunctions, and, further, damages to parts, fires in a worse case, and so on are likely to occur due to spark heat of high energy and the like.
Accordingly, in order to connect an external device to a power supply device in operation, first, the operations of the power supply device are halted to lower a voltage level outputted to the output connectors 26, and, second, the power supply device is turned on after the external device is connected to the output connectors 26, which causes inconvenience.